A fuel cell generally includes a membrane electrode assembly as a power generation module in which electrodes are located on both faces of an electrolyte membrane. The electrodes of the membrane electrode assembly are formed as catalyst electrodes with a catalyst supported therein to accelerate fuel cell reaction. The catalyst electrode is typically formed by applying and drying a catalyst ink in the form of a slurry in which catalyst-supported particles or conductive particles with a catalyst supported thereon and an ionomer are dispersed in an organic solvent or an inorganic solvent (e.g., PTL1).
In order to improve the power generation performance and the durability of the fuel cell, the catalyst electrodes are desired to equalize the power generation distribution on the electrode surface, suppress damage or degradation on the electrode surface and improve the permeability and the diffusivity of a reactive gas. For the improved performance of the catalyst electrodes, the catalyst ink is needed to have structural uniformity, such as uniform dispersion of the catalyst-supported particles, unlikelihood to cause cracking, such as cracks and small holes in the dried state and likelihood to make porous in the dried state.